⚙️ Pump Discharge Pressure Calculator
Calculate the discharge pressure of a pump from total dynamic head (TDH), fluid density, and flow rate. Includes pressure head, elevation head, velocity head, and friction loss breakdown. Supports multiple units and fluid types.
What Is Pump Discharge Pressure?
Pump discharge pressure is the pressure measured at the outlet (discharge) nozzle of a pump while it is actively running. It represents the actual force the pump is exerting to push the liquid out and overcome all downstream resistance, pipe friction, and elevation changes within the system.
The discharge pressure depends on:
- Fluid density (ρ): Denser fluids require more pressure to move.
- Total Dynamic Head (TDH): The total energy the pump must add to the fluid, expressed as an equivalent height of fluid.
- Gravitational acceleration (g): 9.81 m/s² (standard).
Understanding Total Dynamic Head (TDH)
TDH is the sum of four components:
TDH = hp + hz + hv + hf
- hp (Pressure Head): The pressure required at the discharge point (e.g., to force water through sprinklers).
- hz (Elevation Head): The difference in elevation between the pumping water level and the discharge point.
- hv (Velocity Head): The energy due to fluid velocity, given by v²/2g. Usually negligible (keep velocity below 2 m/s).
- hf (Friction Head): The pressure required to overcome friction as water "rubs" against pipe walls and fittings.
How to Calculate Pump Discharge Pressure
The formula to convert TDH to discharge pressure is:
P (kPa) = (ρ × g × TDH) / 1000
where ρ = fluid density (kg/m³), g = 9.81 m/s², TDH = total dynamic head (m)
For example, with water (ρ = 1000 kg/m³) and TDH = 30 m:
P = (1000 × 9.81 × 30) / 1000
P = 294,300 / 1000
P = 294.3 kPa (≈ 42.7 PSI)
Why Use This Calculator?
- Instant results: Get discharge pressure in kPa, PSI, and bar.
- TDH breakdown: Understand each component of total dynamic head.
- Velocity head calculation: Automatically computed from flow rate and pipe diameter.
- Unit flexibility: Supports metric and imperial units for all inputs.
- Free & private: No registration, no data storage — all calculations are done in your browser.
❓ Pump Discharge Pressure FAQ
What is the formula for pump discharge pressure?
The formula is P = (ρ × g × TDH) / 1000, where ρ is fluid density (kg/m³), g is gravity (9.81 m/s²), and TDH is total dynamic head (m). The result is in kPa.
What is the difference between discharge pressure and TDH?
Discharge pressure is the pressure at the pump outlet. Total Dynamic Head (TDH) is the total energy added to the fluid, which includes discharge pressure, suction pressure, and all system losses.
What are the components of TDH?
TDH = hp (pressure head) + hz (elevation head) + hv (velocity head) + hf (friction head).
How is velocity head calculated?
Velocity head is hv = v² / 2g, where v is fluid velocity (m/s) and g is gravity (9.81 m/s²). It is usually negligible for velocities below 2 m/s.
What is the density of water?
Freshwater has a density of approximately 1000 kg/m³ at 4 °C. Seawater is about 1025 kg/m³.
What causes low discharge pressure?
Common causes include: worn impeller, air leaks on the suction side, clogged strainer, closed discharge valve, incorrect rotation direction, or cavitation.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to atmospheric pressure. Absolute pressure = gauge pressure + atmospheric pressure. Pump discharge pressure is typically expressed as gauge pressure.
How accurate is this calculator?
This calculator uses the standard pump discharge pressure formula. Accuracy depends on the precision of the input values, especially the TDH and fluid density. You can adjust the decimal precision in the output.
Is this calculator free?
Yes, this calculator is completely free to use. No registration or personal data storage is required.
What are typical pump discharge pressure values?
Residential water pumps: 200–400 kPa (30–60 PSI). Irrigation systems: 200–500 kPa (30–70 PSI). Industrial pumps: 500–7000 kPa (70–1000 PSI) or higher.